Running speaker wire from amp to X-over

So after doing some reading on here i found out that when running 2 amps in your car, you apparently need to ground them in the same place. I was origionally going to mount my speaker amp under the seat and my sub amp in the trunk but since the grounds need to be as short as possible, it seems like it would be more fesible to mount them in a similar place.

My idea now is to mount both the amps in the trunk, run 1/0 guage back to a distro block in the trunk, then mount the amps next to one another and ground them both under the same rear seat bracket or something of that nature.

Are there any cons to then running rather long sets of speaker wire from the trunk to the x-overs which i plan on mounting under the dash? Will this cause too much resistence in the wire? Are there any better options i have in this matter? Thanks

Also, would it be bad to Run both of my RCA's next to the power wire? Will this cause distortion? I have heard people say it wont and other say it will.